Can Milk Thistle Prevent Skin Cancer?

A compound found in milk thistle, a natural remedy used in traditional healing practices for more than 2,000 years, may offer a new way to prevent skin cancer and heal damage that develops from two types of ultraviolent radiation from sunlight or other sources.

Two University of Colorado Cancer Center studies published this month found that the milk thistle extract, silibinin, kills skin cells mutated by UVA radiation and also protects against damage by UVB radiation.

"When you have a cell affected by UV radiation, you either want to repair it or kill it so that it cannot go on to cause cancer,” said researcher Rajesh Agarwal, a cancer prevention specialist at the CU Cancer Center and professor at the Skaggs School of Pharmacy and Pharmaceutical Sciences. “We show that silibinin does both."

One study, published in the journal Photochemistry and Photobiology, found silibinin was able to target and kill UVA-damaged human skin cells that can cause skin cancer, without harming normal tissues. "When you take human skin cells — keratinocytes — and treat them with silibinin, nothing happens. It's not toxic. But when you damage these cells with UVA radiation, treatment with silibinin kills the cells," Agarwal said.

The second study, published by the same authors in the journal Molecular Carcinogenesis, found silibinin also protects human skill cells from damage by UVB radiation.

Milk thistle products and extracts have long been used medicinally, most commonly to treat liver and gallbladder disorders, and are popular in Europe and the United States.

Agarwal said the new research caps nearly two decades of scientific work with silibinin and that future studies are planned to test its effectiveness in cancer prevention and treatment.

"It has been 20 years of work with this compound, silibinin," Agarwal said. "We first noticed its effectiveness in treating both skin and solid cancers, and we now have a much more complete picture of the mechanisms that allow this compound to work."